LL6.0 installs but after update get X.509 error @boot; LL6.6 install screws PC

[Alan_Wilts]

The inference from posts #1 and #3 is that converting the ext4 data partition (or maybe updating kernel) triggers the system to fail to boot with a specific x509 error.

Many thanks for looking at this Steve. I came to the same conclusion overnight and have just done the following:

1. Booted to LL 6.6 Live and deleted the shared partition
2. Installed LL 6.6 with using just the / and /home partitions reformatted ext4
3. Booted OK into LL and again into Win11
4. In Win11 formatted the shared partition as NTFS.
3. Booted OK into Win11 and again into LL.
4. In LL ran Install Updates
5. Booted into LL and mounted the shared partition on start and disabled mounting the Win11 System partition
6. Booted into Windows and hid the LL system partition (D and remapped the shared partition for E: to D:
7. In Bios changed back to UEFI boot - secure boot is still disabled.
8. Booted to Macrium Reflect Recovery / PE and made an image copy of the whole SSD

So far with many reboots it's been OK.

After Grub selection an error still flashed for half a second (I'm sure it is the X.509) but continues without a disk check. But I think this warning is different to the boot failure. Looks like formatting the NTFS partition in LL is corrupting it and upsetting Grub/boot. Could the reformatting change/damage the GUID?

So I think I will leave it for now and enjoy LL.